Electronic computing devices have become increasingly important to data computation, analysis and storage in our modern society. Modern direct access storage devices (DASDs), such as hard disk drives (HDDs), are heavily relied on to store mass quantities of data for purposes of future retrieval. As such long term data storage has become increasingly popular, and as the speed of microprocessors has steadily increased over time, the need for HDDs with greater storage capacity to store the increased amount of data has steadily increased.
Consequently, there are seemingly constant development efforts to improve the areal density of the media implemented in hard disk drives, where the areal density is measured as the product of bits per inch (“BPI) and tracks per inch (“TPI”). BPI refers to the number of bits that can be written and later reread per linear inch along a track, whereas TPI refers to the number of individual tracks per radial inch. Advancements in areal density result in very narrow data tracks and, therefore, it becomes more and more difficult to align the read/write head accurately on top of the recording track using conventional servos using a voice coil motor (“VCM”).
In response, microactuators and associated microactuator servo control systems are being developed wherein operation of both the VCM and the microactuator has a dynamic effect on the present location of the read/write head relative to the storage medium. For example, a microactuator may be mounted between the suspension and the slider to which the read/write head is coupled, allowing one more degree of freedom for the read/write head to travel at great accuracy over the storage medium. The VCM actuator is used to quickly move the read/write head of the HDD servo system to a target track, whereas the microactuator is used to fine-tune the read/write head position when it is getting closer to the target.
However, because microactuators typically have a very limited stroke (e.g., a few tracks), there exists a need to carefully handle microactuator saturation, which is a state in which a microactuator is driven beyond its ability to respond based on its transfer function.